Ben & Jerry’s Foundation, the Russell Family Foundation and Eric Schmidt from Google’s foundation have joined a group of other charities in making the move to divest from their fossil fuel holdings. The group represents $1.8 billion in assets and collectively believes they have a fiduciary responsibility to fight climate change by investing only in clean energy companies.

Of course, that’s a drop in the ocean when it comes to global institutional assets, but it does send a message — climate change risk matters to fiduciaries.

It’s not just about saving the planet either – there’s also a financial risk say those who believe we’re sitting on a massive fossil fuel bubble. Why? Because exploiting all of the estimated reserves out there would basically end the world as we know it (i.e., there would be no more clean air to breathe, among other disasters) – hence you could call those securities overvalued.

But while it’s great that some major investors are taking a stand on climate change, there is a much bigger problem at hand.

If the world does kick its fossil fuel habit, how will we keep the lights on?

No one is entirely sure but we do know one thing – it’s going to take a whole lot of money to fix the problem. According to the International Energy Agency, we need an investment in clean energy technologies of at least $5 trillion to get us on the road to a sustainable energy structure that doesn’t rely on fossil fuels.

Divestiture sure does send a strong message to fossil fuel companies. But it pales in comparison to a way bigger problem.

Who’s going to pay for all this?

One idea: what about the fossil fuel industry? This is what private equity manager, Daniel Abbasi proposes here. Sure, we know a lot of fossil fuel companies like BP and Chevron are already dipping their toes into alternative energy sources. But it’s more of a sideshow to the main event: oil, oil, oil.

For Abbasi, a carbon tax framework that diverts revenue back to fossil fuel companies to reinvest in alternative energy sources might just get those companies to take their clean energy research and development more seriously.

That could serve to do a couple of things — secure buy-in from fossil fuel companies on a solution (there would be significant dollars attached).

It might also help to divert a significant amount of capital into low carbon initiatives – about $400 billion a year in his view.

Putting more money in the hands of fossil fuel companies might seem counterintuitive – but many of them already have the capacity and the expertise to get the job done.

Is it the right approach? Look – I’m not 100% sold.

But it does recognize that simply pulling money out of the fossil fuel industry isn’t going to solve climate change. Instead, we need institutions to move towards solutions first, investing collectively in a way to keep the lights on in a world without fossil fuels.

Let’s file this one under long-term investing – wherein asset owners behave like real asset owners and begin managing their game for the long-term.